Application of potassium-modified carbon nitride as a highly efficient recyclable catalyst for synthesis of 4H-chromene derivatives

A potassium-doped carbon nitride (K-CN) was prepared by a simple thermal polymerization method. The prepared K-CN was characterized by Fourier infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. The obtained K-CN exhibited excellent catalytic activity for synthesis of 4H-chromene derivatives via one-pot three-component reaction of salicylaldehyde, cyclohexane-1,3-diones and 4-hydroxycoumarin in water/ethyl lactate at room temperature. The reported method shows significant advantages, such as high yield, mild and clean reaction conditions, the use of recyclable catalyst and ethyl lactate/water as an environmentally friendly solvent, multi-component reaction at room temperature, no chromatographic separation and suitable for large-scale synthesis.